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<a href="session_2shm_2shm__fwd_8hpp.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno">    1</span><span class="comment">/* Flow-IPC: Shared Memory</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno">    2</span><span class="comment"> * Copyright 2023 Akamai Technologies, Inc.</span></div>
<div class="line"><a id="l00003" name="l00003"></a><span class="lineno">    3</span><span class="comment"> *</span></div>
<div class="line"><a id="l00004" name="l00004"></a><span class="lineno">    4</span><span class="comment"> * Licensed under the Apache License, Version 2.0 (the</span></div>
<div class="line"><a id="l00005" name="l00005"></a><span class="lineno">    5</span><span class="comment"> * &quot;License&quot;); you may not use this file except in</span></div>
<div class="line"><a id="l00006" name="l00006"></a><span class="lineno">    6</span><span class="comment"> * compliance with the License.  You may obtain a copy</span></div>
<div class="line"><a id="l00007" name="l00007"></a><span class="lineno">    7</span><span class="comment"> * of the License at</span></div>
<div class="line"><a id="l00008" name="l00008"></a><span class="lineno">    8</span><span class="comment"> *</span></div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno">    9</span><span class="comment"> *   https://www.apache.org/licenses/LICENSE-2.0</span></div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno">   10</span><span class="comment"> *</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno">   11</span><span class="comment"> * Unless required by applicable law or agreed to in</span></div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno">   12</span><span class="comment"> * writing, software distributed under the License is</span></div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno">   13</span><span class="comment"> * distributed on an &quot;AS IS&quot; BASIS, WITHOUT WARRANTIES OR</span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno">   14</span><span class="comment"> * CONDITIONS OF ANY KIND, either express or implied.</span></div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno">   15</span><span class="comment"> * See the License for the specific language governing</span></div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno">   16</span><span class="comment"> * permissions and limitations under the License. */</span></div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno">   17</span><span class="comment"></span> </div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno">   18</span><span class="comment">/// @file</span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno">   19</span><span class="comment"></span><span class="preprocessor">#pragma once</span></div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno">   20</span><span class="comment"></span> </div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno">   21</span><span class="comment">/**</span></div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno">   22</span><span class="comment"> * ipc::session sub-namespace that groups together facilities for SHM-backed sessions, particularly augmenting</span></div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno">   23</span><span class="comment"> * #Client_session, #Server_session, and Session_server classes by providing SHM-backed zero-copy functionality.</span></div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno">   24</span><span class="comment"> * ipc::session::shm is itself empty or almost empty; but for each possible SHM provider there is a further</span></div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno">   25</span><span class="comment"> * sub-namespace; for example ipc::session::shm::classic.</span></div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno">   26</span><span class="comment"> *</span></div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno">   27</span><span class="comment"> * ### Background ###</span></div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno">   28</span><span class="comment"> * ipc::shm provides SHM facilities, including ipc::shm::classic and ipc::shm::arena_lend::jemalloc, that can be used</span></div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno">   29</span><span class="comment"> * stand-alone, without ipc::session.  As with ipc::transport, though, this is not very convenient.</span></div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno">   30</span><span class="comment"> * ipc::session is well integrated with ipc::shm in that it provides certain pre-made arenas and simplifies</span></div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno">   31</span><span class="comment"> * transmission of handles to SHM-constructed objects and allows to place transport::struc::Channel</span></div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno">   32</span><span class="comment"> * out-messages into SHM instead of heap -- achieving full zero-copy if desired.  ipc::session::shm is where</span></div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno">   33</span><span class="comment"> * this support lives.</span></div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno">   34</span><span class="comment"> *</span></div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno">   35</span><span class="comment"> * ### Details ###</span></div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno">   36</span><span class="comment"> * If you want these features, everything in the &quot;Overview of relevant APIs&quot; section (of ipc::session doc header)</span></div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno">   37</span><span class="comment"> * still applies identically, except you shall choose different types rather than #Client_session, #Server_session,</span></div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno">   38</span><span class="comment"> * Session_server.  Firstly decide which SHM-provider; as of this writing ipc::shm::classic::Pool_arena or</span></div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno">   39</span><span class="comment"> * ipc::shm::arena_lend::jemalloc.  For illustration let&#39;s assume you chose the former.  Then:</span></div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno">   40</span><span class="comment"> *   - Use shm::classic::Client_session in place of vanilla #Client_session.</span></div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno">   41</span><span class="comment"> *   - Use shm::classic::Session_server in place of vanilla Session_server.</span></div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno">   42</span><span class="comment"> *     - This will emit shm::classic::Server_session in place of vanilla #Server_session.</span></div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno">   43</span><span class="comment"> *</span></div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno">   44</span><span class="comment"> * We strongly recommend making yourself aliases as shown below, then from that point on obtaining all subsequent</span></div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno">   45</span><span class="comment"> * ipc::session types via aliases contained within those aliases (and then more aliases off those</span></div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno">   46</span><span class="comment"> * aliases as needed).  The idea is to have only one point in the code where the SHM-backing (or no SHM backing)</span></div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno">   47</span><span class="comment"> * of the system are specified (simply by indicating the namespace of the top-level `Session_server` or `Client_session`</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno">   48</span><span class="comment"> * type of choice), so that it can be easily changed to another, a-la generic programming.</span></div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno">   49</span><span class="comment"> *</span></div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno">   50</span><span class="comment"> * Server-side:</span></div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno">   51</span><span class="comment"> *</span></div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno">   52</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno">   53</span><span class="comment"> *   using Session_server = ipc::session::shm::classic::Session_server</span></div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno">   54</span><span class="comment"> *                            &lt;...&gt;; // Compile-time session-configuring knobs go here.</span></div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno">   55</span><span class="comment"> *   // ^-- Substitute shm::arena_lend::jemalloc::Session_server or even non-zero-copy plain Session_server as desired.</span></div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno">   56</span><span class="comment"> *</span></div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno">   57</span><span class="comment"> *   // From this point on, no need to mention `ipc::session` again.  In particular, e.g.:</span></div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno">   58</span><span class="comment"> *</span></div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno">   59</span><span class="comment"> *   using Session = typename Session_server::Server_session_obj;</span></div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno">   60</span><span class="comment"> *   template&lt;typename Message_body&gt;</span></div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno">   61</span><span class="comment"> *   using Structured_channel = typename Session::template Structured_channel&lt;Message_body&gt;;</span></div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno">   62</span><span class="comment"> *</span></div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno">   63</span><span class="comment"> *   // Off we go!  Use the types as needed.</span></div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno">   64</span><span class="comment"> *</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno">   65</span><span class="comment"> *   // ...</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno">   66</span><span class="comment"> *   Session session; // Maybe fill it out with Session_server::async_accept() following this.</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno">   67</span><span class="comment"> *   // ...</span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno">   68</span><span class="comment"> *   Structured_channel&lt;MessageSchemaRootOfTheGods&gt; cool_channel(...);</span></div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno">   69</span><span class="comment"> *   // ...</span></div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno">   70</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno">   71</span><span class="comment"> *</span></div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno">   72</span><span class="comment"> * Client-side:</span></div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno">   73</span><span class="comment"> *</span></div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno">   74</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno">   75</span><span class="comment"> *   using Session = ipc::session::shm::classic::Client_session</span></div>
<div class="line"><a id="l00076" name="l00076"></a><span class="lineno">   76</span><span class="comment"> *                     &lt;...&gt;; // Matching (to server-side) knobs go here.</span></div>
<div class="line"><a id="l00077" name="l00077"></a><span class="lineno">   77</span><span class="comment"> *   // ^-- Substitute shm::arena_lend::jemalloc::Client_session or even non-zero-copy plain Client_session as desired.</span></div>
<div class="line"><a id="l00078" name="l00078"></a><span class="lineno">   78</span><span class="comment"> *</span></div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno">   79</span><span class="comment"> *   // From this point on, no need to mention `ipc::session` again.  In particular, e.g.:</span></div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno">   80</span><span class="comment"> *</span></div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno">   81</span><span class="comment"> *   using Session = typename Session_server::Server_session_obj;</span></div>
<div class="line"><a id="l00082" name="l00082"></a><span class="lineno">   82</span><span class="comment"> *   template&lt;typename Message_body&gt;</span></div>
<div class="line"><a id="l00083" name="l00083"></a><span class="lineno">   83</span><span class="comment"> *   using Structured_channel = typename Session::template Structured_channel&lt;Message_body&gt;;</span></div>
<div class="line"><a id="l00084" name="l00084"></a><span class="lineno">   84</span><span class="comment"> *</span></div>
<div class="line"><a id="l00085" name="l00085"></a><span class="lineno">   85</span><span class="comment"> *   // Off we go!  Use the types as needed.</span></div>
<div class="line"><a id="l00086" name="l00086"></a><span class="lineno">   86</span><span class="comment"> *</span></div>
<div class="line"><a id="l00087" name="l00087"></a><span class="lineno">   87</span><span class="comment"> *   // ...</span></div>
<div class="line"><a id="l00088" name="l00088"></a><span class="lineno">   88</span><span class="comment"> *   Session session(...); // Maybe .sync_connect() following this.</span></div>
<div class="line"><a id="l00089" name="l00089"></a><span class="lineno">   89</span><span class="comment"> *   // ...</span></div>
<div class="line"><a id="l00090" name="l00090"></a><span class="lineno">   90</span><span class="comment"> *   Structured_channel&lt;MessageSchemaRootOfTheGods&gt; cool_channel(...);</span></div>
<div class="line"><a id="l00091" name="l00091"></a><span class="lineno">   91</span><span class="comment"> *   // ...</span></div>
<div class="line"><a id="l00092" name="l00092"></a><span class="lineno">   92</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00093" name="l00093"></a><span class="lineno">   93</span><span class="comment"> *</span></div>
<div class="line"><a id="l00094" name="l00094"></a><span class="lineno">   94</span><span class="comment"> * Entering PEER state is exactly identical to the vanilla APIs (the differences are under the hood).</span></div>
<div class="line"><a id="l00095" name="l00095"></a><span class="lineno">   95</span><span class="comment"> * Once in PEER state, however, the added capabilities become available; these are on top of</span></div>
<div class="line"><a id="l00096" name="l00096"></a><span class="lineno">   96</span><span class="comment"> * the Session concept API, in the form added members including methods.  A quick survey:</span></div>
<div class="line"><a id="l00097" name="l00097"></a><span class="lineno">   97</span><span class="comment"> *   - Each of shm::classic::Client_session and shm::classic::Server_session is a shm::classic::Session_mv</span></div>
<div class="line"><a id="l00098" name="l00098"></a><span class="lineno">   98</span><span class="comment"> *     (alias and sub-class respectively).  shm::classic::Session::session_shm() and</span></div>
<div class="line"><a id="l00099" name="l00099"></a><span class="lineno">   99</span><span class="comment"> *     shm::classic::Session::app_shm() each access the pre-made SHM arenas of the aforementioned scopes</span></div>
<div class="line"><a id="l00100" name="l00100"></a><span class="lineno">  100</span><span class="comment"> *     (per-session and per-app respectively). Call `construct&lt;T&gt;(...)` on either to SHM-construct an object.</span></div>
<div class="line"><a id="l00101" name="l00101"></a><span class="lineno">  101</span><span class="comment"> *     Use an STL-compliant `T` with `Session::Allocator` and shm::stl::Arena_activator aids to store</span></div>
<div class="line"><a id="l00102" name="l00102"></a><span class="lineno">  102</span><span class="comment"> *     sophisticated data structures in SHM.  Use shm::classic::Session_mv::lend_object() to prepare to</span></div>
<div class="line"><a id="l00103" name="l00103"></a><span class="lineno">  103</span><span class="comment"> *     transmit an outer SHM-handle to such a `T` to the opposing shm::classic::Session.  On that side use</span></div>
<div class="line"><a id="l00104" name="l00104"></a><span class="lineno">  104</span><span class="comment"> *     shm::classic::Session_mv::borrow_object() to recover an equivalent outer SHM-handle.  The `T` shall be</span></div>
<div class="line"><a id="l00105" name="l00105"></a><span class="lineno">  105</span><span class="comment"> *     returned to the SHM-arena once *both* processes are done with it. The handle acts like a</span></div>
<div class="line"><a id="l00106" name="l00106"></a><span class="lineno">  106</span><span class="comment"> *     cross-process-GCing `shared_ptr` (and is, in fact, `shared_ptr&lt;T&gt;`).</span></div>
<div class="line"><a id="l00107" name="l00107"></a><span class="lineno">  107</span><span class="comment"> *     - This enables manually-constructing structures and transmitting them from one session participant to the</span></div>
<div class="line"><a id="l00108" name="l00108"></a><span class="lineno">  108</span><span class="comment"> *       other.</span></div>
<div class="line"><a id="l00109" name="l00109"></a><span class="lineno">  109</span><span class="comment"> *     - On the borrower side one should define `T` in terms of `&quot;Session::Borrower_allocator&quot;` instead of</span></div>
<div class="line"><a id="l00110" name="l00110"></a><span class="lineno">  110</span><span class="comment"> *       `&quot;Session::Allocator&quot;`.  (With SHM-classic they are the same type; but with arena-lending SHM providers,</span></div>
<div class="line"><a id="l00111" name="l00111"></a><span class="lineno">  111</span><span class="comment"> *       SHM-jemalloc at the moment, they are not.)</span></div>
<div class="line"><a id="l00112" name="l00112"></a><span class="lineno">  112</span><span class="comment"> *   - Suppose you have opened a channel C between your two peer objects.  Suppose you upgrade it to a</span></div>
<div class="line"><a id="l00113" name="l00113"></a><span class="lineno">  113</span><span class="comment"> *     transport::struc::Channel.  Without SHM, your only out-of-the-box choice for out-message serialization</span></div>
<div class="line"><a id="l00114" name="l00114"></a><span class="lineno">  114</span><span class="comment"> *     is the heap (transport::struc::Channel_base::Serialize_via_heap-tag ctor).  This involves copying into</span></div>
<div class="line"><a id="l00115" name="l00115"></a><span class="lineno">  115</span><span class="comment"> *     and out of the low-level IPC transport.  With SHM you can now do better: as you mutate your out-message,</span></div>
<div class="line"><a id="l00116" name="l00116"></a><span class="lineno">  116</span><span class="comment"> *     it will be invisibly backed by SHM-allocated segment(s); and when you `send()` and receive it, only</span></div>
<div class="line"><a id="l00117" name="l00117"></a><span class="lineno">  117</span><span class="comment"> *     a small handle will be copied into and out of the IPC transport (again invisibly to you; it&#39;ll just happen).</span></div>
<div class="line"><a id="l00118" name="l00118"></a><span class="lineno">  118</span><span class="comment"> *     To set it up simply use `transport::struc::Channel_base::Serialize_via_session_shm`-tag</span></div>
<div class="line"><a id="l00119" name="l00119"></a><span class="lineno">  119</span><span class="comment"> *     (or possibly `Serialize_via_app_shm`-tag) ctor of `struc::Channel`.</span></div>
<div class="line"><a id="l00120" name="l00120"></a><span class="lineno">  120</span><span class="comment"> *     - This enables zero-copy-enabled/arbitrarily-large structured messages through channels in your</span></div>
<div class="line"><a id="l00121" name="l00121"></a><span class="lineno">  121</span><span class="comment"> *       shm::classic::Client_session&lt;-&gt;shm::classic::Server_session session.</span></div>
<div class="line"><a id="l00122" name="l00122"></a><span class="lineno">  122</span><span class="comment"> *</span></div>
<div class="line"><a id="l00123" name="l00123"></a><span class="lineno">  123</span><span class="comment"> * That&#39;s with SHM-classic.  With SHM-jemalloc it is all quite similar; basically just replace `classic` with</span></div>
<div class="line"><a id="l00124" name="l00124"></a><span class="lineno">  124</span><span class="comment"> * `arena_lend::jemalloc` in various names above (more or less).</span></div>
<div class="line"><a id="l00125" name="l00125"></a><span class="lineno">  125</span><span class="comment"> * Reminder: it is easiest and most stylish to not have to a big search/replace but rather to use the</span></div>
<div class="line"><a id="l00126" name="l00126"></a><span class="lineno">  126</span><span class="comment"> * top-level alias technique shown in the above code snippets.</span></div>
<div class="line"><a id="l00127" name="l00127"></a><span class="lineno">  127</span><span class="comment"> *</span></div>
<div class="line"><a id="l00128" name="l00128"></a><span class="lineno">  128</span><span class="comment"> * Further details about SHM-classic versus SHM-jemalloc (etc.) are documented elsewhere.</span></div>
<div class="line"><a id="l00129" name="l00129"></a><span class="lineno">  129</span><span class="comment"> * Preview: `arena_lend::jemalloc` is safer and faster (backed by the commercial-grade &quot;jemalloc&quot; `malloc()` impl</span></div>
<div class="line"><a id="l00130" name="l00130"></a><span class="lineno">  130</span><span class="comment"> * algorithm),  though it does not allow `app_shm()-&gt;construct()` (per-app-scope allocation) on the client side (via</span></div>
<div class="line"><a id="l00131" name="l00131"></a><span class="lineno">  131</span><span class="comment"> * shm::arena_lend::jemalloc::Client_session -- available only shm::arena_lend::jemalloc::Server_session); there&#39;s</span></div>
<div class="line"><a id="l00132" name="l00132"></a><span class="lineno">  132</span><span class="comment"> * no such method as `shm::arena_lend::jemalloc::Client_session::app_shm()`.</span></div>
<div class="line"><a id="l00133" name="l00133"></a><span class="lineno">  133</span><span class="comment"> *</span></div>
<div class="line"><a id="l00134" name="l00134"></a><span class="lineno">  134</span><span class="comment"> * ### One more small thing: logging addendum for SHM-jemalloc users ###</span></div>
<div class="line"><a id="l00135" name="l00135"></a><span class="lineno">  135</span><span class="comment"> * This is really a footnote in importance, though there&#39;s no good reason to ignore it either.</span></div>
<div class="line"><a id="l00136" name="l00136"></a><span class="lineno">  136</span><span class="comment"> * A certain aspect of SHM-jemalloc (and potentially more future arena-lending-type SHM-providers) requires</span></div>
<div class="line"><a id="l00137" name="l00137"></a><span class="lineno">  137</span><span class="comment"> * singleton-based (essentially, global) operation.  You need not worry about it... it just works... except</span></div>
<div class="line"><a id="l00138" name="l00138"></a><span class="lineno">  138</span><span class="comment"> * it (like all Flow-IPC code) logs; and thus needs to know to which `Logger` to log.  Since various ipc::session</span></div>
<div class="line"><a id="l00139" name="l00139"></a><span class="lineno">  139</span><span class="comment"> * objects don&#39;t want to presume whose `Logger` is the one to impose on this shared global guy -- plus the</span></div>
<div class="line"><a id="l00140" name="l00140"></a><span class="lineno">  140</span><span class="comment"> * setter is not thread-safe -- we ask that you do so sometime before any ipc::session::arena_lend object creation.</span></div>
<div class="line"><a id="l00141" name="l00141"></a><span class="lineno">  141</span><span class="comment"> * Namely just do this:</span></div>
<div class="line"><a id="l00142" name="l00142"></a><span class="lineno">  142</span><span class="comment"> *</span></div>
<div class="line"><a id="l00143" name="l00143"></a><span class="lineno">  143</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00144" name="l00144"></a><span class="lineno">  144</span><span class="comment"> *   ipc::session::shm::arena_lend::Borrower_shm_pool_collection_repository_singleton::get_instance()</span></div>
<div class="line"><a id="l00145" name="l00145"></a><span class="lineno">  145</span><span class="comment"> *     .set_logger(...); // ... = pointer to your Logger of choice.  Null to disable logging (which is default anyway).</span></div>
<div class="line"><a id="l00146" name="l00146"></a><span class="lineno">  146</span><span class="comment"> *   ~~~</span></div>
<div class="line"><a id="l00147" name="l00147"></a><span class="lineno">  147</span><span class="comment"> *</span></div>
<div class="line"><a id="l00148" name="l00148"></a><span class="lineno">  148</span><span class="comment"> * If SHM-jemalloc is not used, this call is harmless.</span></div>
<div class="line"><a id="l00149" name="l00149"></a><span class="lineno">  149</span><span class="comment"> */</span></div>
<div class="line"><a id="l00150" name="l00150"></a><span class="lineno">  150</span><span class="keyword">namespace </span><a class="code hl_namespace" href="namespaceipc_1_1session_1_1shm.html">ipc::session::shm</a></div>
<div class="line"><a id="l00151" name="l00151"></a><span class="lineno">  151</span>{</div>
<div class="line"><a id="l00152" name="l00152"></a><span class="lineno">  152</span> </div>
<div class="line"><a id="l00153" name="l00153"></a><span class="lineno">  153</span><span class="comment">// Types.</span></div>
<div class="line"><a id="l00154" name="l00154"></a><span class="lineno">  154</span> </div>
<div class="line"><a id="l00155" name="l00155"></a><span class="lineno">  155</span><span class="comment">// Find doc headers near the bodies of these compound types.</span></div>
<div class="line"><a id="l00156" name="l00156"></a><span class="lineno">  156</span> </div>
<div class="line"><a id="l00157" name="l00157"></a><span class="lineno">  157</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> Arena&gt;</div>
<div class="line"><a id="l00158" name="l00158"></a><span class="lineno">  158</span><span class="keyword">struct </span>Arena_to_shm_session;</div>
<div class="line"><a id="l00159" name="l00159"></a><span class="lineno">  159</span> </div>
<div class="line"><a id="l00160" name="l00160"></a><span class="lineno">  160</span>} <span class="comment">// namespace ipc::session::shm</span></div>
<div class="ttc" id="anamespaceipc_1_1session_1_1shm_html"><div class="ttname"><a href="namespaceipc_1_1session_1_1shm.html">ipc::session::shm</a></div><div class="ttdoc">ipc::session sub-namespace that groups together facilities for SHM-backed sessions,...</div><div class="ttdef"><b>Definition:</b> <a href="session_2detail_2shm_2classic_2classic__fwd_8hpp_source.html#l00023">classic_fwd.hpp:24</a></div></div>
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